JP6844215B2 - 2-flute ball end mill - Google Patents

Description

The present invention relates to a two-flute ball end mill in which two bottom blades are formed at the tip of an end mill body that is rotated around an axis.

In such a two-flute ball end mill, for example, in Patent Document 1, for machining a high-hardness material such as a mold, a plurality of cutting edges and a plurality of cutting edges are formed on the axial tip side of the tool body in the rotation direction. A cutting edge portion having a gash formed between adjacent cutting edges is provided, and this cutting edge portion forms a ball blade portion in which a ball blade is formed and an outer peripheral blade continuous with the ball blade in the axial direction of the tool body. It is a ball end mill divided into an outer peripheral blade portion to be formed, and the ball blade portion is continuously formed on the second surface formed on the rear side in the rotation direction of the ball blade and the second surface formed on the rear side in the rotation direction. , It has a third surface that is different from the second surface, and a fourth surface that is continuously formed on this third surface on the rear side in the rotation direction and forms a surface different from the third surface, and each outer circumference of the outer peripheral blade portion. A plurality of outer peripheral blade relief surfaces forming different surfaces are formed on the rear side in the rotation direction of the blade, and the fourth surface is formed in a curved shape that is convex toward the outer peripheral side with respect to the rotation axis, and is formed on the outer peripheral blade side of the gash. It has been proposed that an outer peripheral groove leading to the gash is formed, and the groove bottom of the gash and the groove bottom of the outer peripheral groove form different angles with respect to the rotation axis.

In such a two-flute ball end mill, the ball blade portion has different flanks (second surface, third surface, fourth surface) continuously formed on the rear side in the rotation direction of the ball blade, and the outer peripheral blade. A plurality of outer peripheral blade relief surfaces forming different surfaces are also formed on the rear side in the rotation direction of each outer peripheral blade, and the outer shapes of these ball blades and the outer peripheral blades are rotated around the rotation axis of the ball end mill. It is easy to form a three-dimensional shape close to the body shape, and the rigidity of the cutting edge portion can be increased.

Japanese Unexamined Patent Publication No. 2015-182196

By the way, in the two-flute ball end mill described in Patent Document 1, the gashes are continuously different surfaces in order toward the side opposite to the rotation direction of the end mill, that is, a gash wall surface, a gash bottom surface, and a ball blade. It is composed of a rake face, but on the end mill rotation center side of the tip of the end mill body, the bottom surface of the gash and the rake face only intersect the inner peripheral end of the ball blade. For this reason, the chips generated near the inner peripheral end of the ball blade lose their place and easily cause chip clogging, which leads to an increase in cutting resistance or when processing a hard material such as a cemented carbide. May cause a defect around the center of rotation of the end mill at the tip of the end mill body.

The present invention has been made under such a background. For example, in a two-flute ball end mill for processing a hard material as described above, the chip evacuation property around the inner peripheral end of the bottom blade (ball blade). It is an object of the present invention to provide a two-flute ball end mill capable of preventing an increase in cutting resistance due to chip clogging and a chipping of the end mill body around the center of rotation of the end mill by improving the quality.

In order to solve the above problems and achieve such an object, in the present invention, a pair of gashes are formed at the tip of the end mill body rotated around the axis in a 180 ° rotational symmetry with respect to the axis. The rotation locus around the axis has a center on the axis at the intersection ridge of the bottom surface of the gash facing the end mill rotation direction of the gash and the tip flank extending from the bottom surface of the gash to the side opposite to the end mill rotation direction. A two-flute ball end mill in which bottom blades having a convex hemispherical shape that are convex on the tip side of the end mill body are formed, and the gash is a first that intersects the bottom surface of the gash and extends in the end mill rotation direction. A second gash wall surface that intersects the first gash wall surface and further extends in the end mill rotation direction, and the pair of the bottom blades are from the outer peripheral side to the inner peripheral side of the tip end portion of the end mill main body. Beyond the center of rotation of the end mill at the tip of the main body of the end mill, it extends so as to cross each other at intervals and reaches the inner peripheral end of the bottom blade, and intersects the first and second gash wall surfaces. The ridge line and the intersecting ridge line between the second gosh wall surface and the tip flank surface are formed so as to intersect at the inner peripheral end of the bottom blade, and are formed to intersect with the bottom blade when viewed from the tip side in the axial direction. The intersection angle of the bottom blade with the intersecting ridgeline of the first and second gosh wall surfaces intersecting at the inner peripheral end is in the range of 20 ° to 50 ° .

In the two-flute ball end mill configured in this way, the gash intersects the first gash wall surface that intersects the bottom surface of the gash that is the rake surface of the bottom blade and extends in the direction of rotation of the end mill, and the first gash wall surface. A second gash wall surface is provided, and the second gash wall surface extends further in the end mill rotation direction from the first gash wall surface, and thus is similar to the two-flute ball end mill described in Patent Document 1. , The outer shape of the tip of the end mill body can be made into a three-dimensional shape close to the shape of a rotating body centered on the axis, and high rigidity can be ensured.

The second gash wall surface is formed so that the intersecting ridge line with the first gash wall surface and the intersecting ridge line with the tip flank surface intersect at the inner peripheral end of the bottom blade, that is, the bottom blade. The inner peripheral end serves as the starting point of the first and second gosh wall surfaces around the end mill rotation center at the tip of the end mill body. Therefore, the chips generated around the inner peripheral end of the bottom blade can be quickly discharged from the first gash wall surface through the second gash wall surface, improving the chip discharge property and causing chip clogging. Since it is possible to prevent the occurrence, it is possible to prevent an increase in cutting resistance and a loss of the end mill main body around the center of rotation of the end mill.

Further, by intersecting the first gash wall surface and the second gash wall surface so as to be convex in a cross section orthogonal to the axis line, the outer shape of the tip portion of the end mill main body is a rotating body centered on the axis line. Since the three-dimensional shape is closer to the shape, the rigidity can be further improved.

Further, by forming the first gash wall surface and the second gash wall surface so as to gradually widen as the distance from the inner peripheral end of the bottom blade increases, the end mill main body is formed from the inner circumference of the tip portion to the outer peripheral side of the rear end. The chip discharge space can be increased toward the surface, and the chip discharge property can be further improved.

When viewed from the tip side in the axial direction, the intersection angle between the bottom blade and the intersecting ridgeline of the first and second gash wall surfaces intersecting at the inner peripheral end of the bottom blade is 20 ° to 50 °. It is desirable to be in the range. If this intersection angle is smaller than the above range, the chip discharge space on the inner peripheral end side of the bottom blade may become small, and it may be difficult to sufficiently improve the chip discharge property, which is larger than the above range. And the tip of the end mill body may be severely cut out by the gash, resulting in insufficient rigidity.

Further, by coating the surface of at least the tip of the end mill body with a hard film, particularly a diamond coating, wear of the tip of the end mill body can be suppressed even in the processing of a hard material such as cemented carbide, and the wear of the tip of the end mill body can be suppressed for a long period of time. It is possible to provide a two-flute ball end mill having a longer life and capable of stable machining.

As described above, according to the present invention, it is possible to prevent the occurrence of chip clogging by improving the chip evacuation property around the inner peripheral end of the bottom blade while ensuring the rigidity of the tip of the end mill body, and cutting. It is possible to suppress an increase in resistance and prevent the end mill body from being damaged around the center of rotation of the end mill.

It is an enlarged front view which looked at the tip end part of the end mill main body which shows one Embodiment of this invention from the tip side in the axial direction. It is a side view of the tip end part of the end mill main body of the embodiment shown in FIG. It is a perspective view which looked at the tip end part of the end mill main body of the embodiment shown in FIG. It is a ZZ enlarged sectional view in FIG.

1 to 4 show an embodiment of a two-flute ball end mill of the present invention. In the present embodiment, the end mill main body 1 is formed of a hard material such as cemented carbide in a multi-stage approximately columnar shape centered on the axis O, and its tip portion (the right portion in FIGS. 2 and 3) is cut with a small diameter. The blade portion 2 is formed, and the rear end side (left side in FIGS. 2 and 3) of the cutting blade portion 2 is a large-diameter columnar shank portion (not shown) via the neck portion 3 whose outer diameter gradually increases. To. In such a two-flute ball end mill, the shank portion is attached to the spindle of the machine tool, and while being rotated around the axis O in the end mill rotation direction T, the shank portion is sent out in a direction intersecting the axis O, and the cutting edge portion 2 Is used to cut hard materials such as cemented carbide.

A pair of concave groove-shaped gashes 4 are provided on the cutting edge portion 2 of the tip end portion of the end mill body 1 from the periphery of the end mill rotation center located on the axis O of the tip end portion of the cutting edge portion 2 to the outer peripheral side of the rear end of the cutting edge portion 2. It is formed 180 ° rotationally symmetric with respect to the axis O so as to extend toward. These gashes 4 intersect the bottom surface 4a of the gash extending from the outer periphery of the cutting edge portion 2 toward the inner circumference side in the rotation direction T of the end mill in order toward the rotation direction T of the end mill and the inner circumference side of the bottom surface 4a of the gash. A first gash wall surface 4b extending in the end mill rotation direction T and a second gash wall surface 4c intersecting the first gash wall surface 4b and further extending in the end mill rotation direction T are provided.

Further, a tip flank surface 5 is formed between the two gashes 4 in the circumferential direction of the cutting edge portion 2. In the present embodiment, the tip flank surface 5 also has a first direction extending from the gash 4 toward the side opposite to the end mill rotation direction T, intersecting the gash bottom surface 4a of the gash 4 and extending in the direction opposite to the end mill rotation direction T. An obtuse angle to the tip flank 5a, a second tip flank 5b that intersects the first tip flank 5a at an obtuse angle and extends in the direction opposite to the end mill rotation direction T, and the second tip flank 5b. It is provided with a third tip flank surface 5c that intersects with and extends to the side opposite to the end mill rotation direction T.

Further, an axis O is formed at the intersection ridge line portion between the gash bottom surface 4a of the gash 4 and the first tip flank surface 5a of the tip flank surface 5 extending from the outer peripheral edge of the gash bottom surface 4a to the side opposite to the end mill rotation direction T. A bottom blade 6 having a convex hemispherical shape whose rotation locus has a center on the axis O and is convex toward the tip end side of the end mill main body 1 is formed. Here, the pair of bottom blades 6 formed on the outer peripheral edge of the gash bottom surface 4a of the pair of gashes 4 are directed from the outer peripheral side to the inner peripheral side of the cutting edge portion 2 at the tip of the end mill main body 1 as shown in FIG. It extends beyond the center of rotation of the end mill at the tip of the cutting edge portion 2 so as to cross each other at intervals and reaches the inner peripheral end S of the bottom blade 6. Further, a chisel 7 passing through the center of rotation of the end mill is formed at the intersecting ridge line portion between the first tip flanks 5a of the pair of bottom blades 6.

Further, in the cutting edge portion 2, the portion on the rear end side of the portion where the rotation locus of the bottom blade 6 has a convex hemispherical shape extends in a substantially columnar shape centered on the axis O and is connected to the tip of the neck portion 3. The gash 4 is continuous with this portion, and an outer peripheral relief surface 8 connected to the tip relief surface 5 is formed on the side opposite to the end mill rotation direction T from the outer peripheral edge of the continuous gash bottom surface 4a of the gash 4. An outer peripheral blade 9 connected to the outer peripheral end of the bottom blade 6 is formed at the intersecting ridge line portion between the outer peripheral flank surface 8 and the bottom surface 4a of the gash.

The bottom blade 6 and the outer peripheral blade 9 are formed so as to twist in the direction opposite to the end mill rotation direction T from the inner peripheral end S of the bottom blade 6 toward the outer peripheral side of the rear end. Further, as shown in FIGS. 2 and 3, the first gash wall surface 4b of the gash 4 extends to the neck portion 3 and is cut off, whereby the gash 4 and the tip flank surface 5, the outer peripheral flank surface 8 and the bottom blade 6 are cut off. The surfaces of at least the cutting edge portion 2 and the neck portion 3 on which the outer peripheral blade 9 is formed, preferably the entire surface of the end mill main body 1, are coated with a hard film, more preferably a diamond coating.

Then, around the end mill rotation center at the tip of the cutting edge portion 2, the cross ridge line L1 of the first and second gash wall surfaces 4b and 4c of the gash 4 and the cross ridge line L2 between the second gash wall surface 4c and the tip flank surface 5 are formed. Is formed so as to intersect at the inner peripheral end S of the bottom blade 6 as shown in FIG. Here, as shown in FIG. 1, when viewed from the tip side in the O-direction of the axis, the bottom blade 6 and the intersecting ridge line L1 of the first and second gash wall surfaces 4b and 4c intersecting at the inner peripheral end S of the bottom blade 6. The intersection angle α with is in the range of 20 ° to 50 °, and the intersection of the second gash wall surface 4c and the tip flank 5 (first tip flank 5a) intersects the ridgeline L2 and the bottom blade 6. The angle β is in the range of 60 ° to 120 °.

Further, as shown in FIG. 4, the first gash wall surface 4b and the second gash wall surface 4c of the gash 4 intersect with each other so as to be convex at an obtuse angle in a cross section orthogonal to the axis O, and the bottom blade 6 It is formed so as to gradually widen in the circumferential direction as it is separated from the inner peripheral end S of the above. Further, the second gosh wall surface 4c is formed so as to intersect all of the first to third tip flanks 5a to 5c of the tip flank 5 as shown in FIG. 1, and the intersecting ridge line L2 is the bottom blade. It is formed in a polygonal line shape that bends in multiple steps toward the side opposite to the end mill rotation direction T as the distance from the inner peripheral end S of No. 6 increases. The third tip flank surface 5c is substantially flat.

In the two-flute ball end mill configured as described above, the gash 4 intersects the bottom surface 4a of the gash, which is the rake face of the bottom blade 6, and extends in the end mill rotation direction T, and the first gash wall surface 4b and the first gash wall surface 4b. A second gash wall surface 4c that intersects the gash wall surface 4b and extends further in the end mill rotation direction T is provided, whereby the outer shape of the cutting edge portion 2 at the tip of the end mill body 1 is rotated about the axis O. It can be a three-dimensional shape close to the body shape.

In particular, in the present embodiment, since the first gash wall surface 4b and the second gash wall surface 4c are intersected so as to be convex in a cross section orthogonal to the axis O, the outer shape of the cutting edge portion 2 is the axis. The three-dimensional shape is closer to the shape of a rotating body centered on O. Therefore, a sufficient wall thickness of the end mill main body 1 can be secured on the side of the bottom blade 6 and the outer peripheral blade 9 opposite to the end mill rotation direction T, and the rigidity of the cutting edge portion 2 can be improved.

On the other hand, in the two-flute ball end mill having the above configuration, the crossing ridge line L1 of the first and second gash wall surfaces 4b and 4c and the crossing ridge line L2 of the second gash wall surface 4c and the tip flank surface 5 are formed. It is formed so as to intersect at the inner peripheral end S of the bottom blade 6. Therefore, the inner peripheral end S of the bottom blade 6 becomes the starting point of the first and second gash wall surfaces 4b and 4c around the end mill rotation center at the tip of the cutting edge portion 2.

Therefore, the chips generated around the inner peripheral end S of the bottom blade 6 can be quickly discharged from the first gash wall surface 4b through the second gash wall surface 4c, improving the chip discharge property. It is possible to prevent the occurrence of chip clogging. Therefore, according to the two-flute ball end mill having the above configuration, it is possible to prevent an increase in cutting resistance due to such chip clogging and a chipping of the end mill main body 1 around the center of rotation of the end mill, which is similar to that of cemented carbide. It is possible to perform stable processing on hard materials over a long period of time.

Further, in the present embodiment, the first gash wall surface 4b and the second gash wall surface 4c are formed so as to gradually widen in the circumferential direction as the distance from the inner peripheral end S of the bottom blade 6 increases. As a result, the chip discharge space created by the gash 4 can be increased from the inner circumference of the tip portion of the cutting edge portion 2 around the center of rotation of the end mill toward the outer circumference side of the rear end portion. Therefore, it is possible to further improve the chip evacuation property, and it is possible to more reliably prevent an increase in cutting resistance and the occurrence of defects due to chip clogging.

Further, in the present embodiment, the crossing angle α between the bottom blade 6 and the crossing ridges L1 of the first and second gash wall surfaces 4b and 4c when viewed from the tip side in the O direction of the axis is in the range of 20 ° to 50 °. This also makes it possible to secure the rigidity of the cutting edge portion 2 while improving the chip evacuation property. That is, if this crossing angle α is smaller than the above range, the chip discharge space on the inner peripheral end S side of the bottom blade 6 may become small, and it may be difficult to sufficiently improve the chip discharge property. If the crossing angle α is larger than the above range, the cutting edge portion 2 is largely cut out by the gash 4, which may lead to insufficient rigidity.

Similarly, in the present embodiment, the cross ridge line L2 and the bottom blade 6 of the second gosh wall surface 4c and the tip flank surface 5 (first tip flank surface 5a) when viewed from the tip side in the O direction of the axis line. Since the crossing angle β is in the range of 60 ° to 120 °, it is possible to secure the rigidity of the cutting edge portion 2 while also improving the chip evacuation property. That is, even if the crossing angle β is smaller than the above range, the chip discharging space on the inner peripheral end S side of the bottom blade 6 may become small, and it may be difficult to sufficiently improve the chip discharging property. Even if the angle β is larger than the above range, the cutting edge portion 2 may have insufficient rigidity. The crossing angle β is more preferably in the range of 60 ° to 120 °.

Furthermore, in the present embodiment, at least the surfaces of the cutting edge portion 2 and the neck portion 3 which are the tip portions of the end mill main body 1 are coated with a hard film, preferably a diamond coating. Therefore, even in the processing of a hard material such as cemented carbide, the wear of the cutting edge portion 2 can be suppressed, so that stable processing can be performed over a longer period of time.

1 End mill body 2 Cutting edge 3 Neck 4 Gash 4a Gash bottom surface 4b 1st gash wall surface 4c 2nd gash wall surface 5 Tip flank 5a 1st tip flank 5b 2nd tip flank 5c 3rd tip flank Surface 6 Bottom blade 7 Chisel 8 Outer peripheral escape surface 9 Outer blade O End mill body 1 axis T End mill rotation direction S Inner peripheral end of bottom blade 6 L1 1st and 2nd gosh wall surface 4b, 4c cross ridge line L2 2nd Crossing ridge line between the gash wall surface 4c and the outer peripheral flank surface α The intersection angle between the bottom blade 6 and the crossing ridge line L1 when viewed from the tip side in the O direction of the axis line Crossing angle with ridge line L2

Claims (5)

A pair of gashes are formed at the tip of the end mill body that is rotated around the axis in a 180 ° rotational symmetry with respect to the above axis, and the bottom surface of these gashes facing the end mill rotation direction and the bottom surface of the end mill opposite to the end mill rotation direction. A bottom blade having a convex hemispherical shape, in which the rotation locus around the axis has a center on the axis and is convex toward the tip of the end mill body, is formed at the intersection ridge with the tip flank extending to the side. It is a 2-flute ball end mill that has been made.
The gash includes a first gash wall surface that intersects the bottom surface of the gash and extends in the end mill rotation direction, and a second gash wall surface that intersects the first gash wall surface and further extends in the end mill rotation direction.
The pair of bottom blades extend from the outer peripheral side of the tip end portion of the end mill main body toward the inner peripheral side beyond the end mill rotation center of the tip end portion of the end mill main body and extend so as to cross each other at intervals. Has reached the inner peripheral edge of
The intersecting ridges of the first and second gash wall surfaces and the intersecting ridges of the second gash wall surface and the tip flank surface are formed so as to intersect at the inner peripheral end of the bottom blade .
When viewed from the tip side in the axial direction, the intersection angle between the bottom blade and the intersecting ridgeline of the first and second gash wall surfaces intersecting at the inner peripheral end of the bottom blade is in the range of 20 ° to 50 °. A 2-flute ball end mill characterized by being made. The two-flute ball end mill according to claim 1, wherein the first gash wall surface and the second gash wall surface intersect with each other so as to be convex in a cross section orthogonal to the axis line. The first or second aspect of the invention, wherein the first gash wall surface and the second gash wall surface are formed so as to gradually widen as the distance from the inner peripheral end of the bottom blade increases. 2-flute ball end mill. The two-flute ball end mill according to any one of claims 1 to 3 , wherein the surface of at least the tip of the end mill body is coated with a hard film. The two-flute ball end mill according to claim 4 , wherein the hard film is a diamond coating.

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